Make widgets.TextBox work also when embedding.

anntzer · anntzer · commit 1c6d5a1b7f53 · 2020-04-14T10:03:57.000+02:00
When embedding, `canvas.manager` may be None, but we may still have
registered the default key_press_handler (see e.g. the
embedding_in_tk_sgskip.py example), so we still need to disable the
keymap rcParams.

In order to avoid duplicating the logic as to whether use
toolmanager-cleanup in two places (and avoid things going out of sync
between begin_typing and stop_typing), register the cleanup actions
in begin_typing.

Example:
```
from matplotlib.backend_bases import key_press_handler
from matplotlib.backends.backend_qt5agg import FigureCanvas, NavigationToolbar2QT
from matplotlib.backends.qt_compat import QtCore, QtWidgets
from matplotlib.figure import Figure
from matplotlib.widgets import TextBox

class ApplicationWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        canvas = FigureCanvas(Figure(figsize=(5, 3)))
        canvas.setFocusPolicy(QtCore.Qt.StrongFocus)
        self.setCentralWidget(canvas)
        tb = NavigationToolbar2QT(canvas, self)
        self.addToolBar(tb)
        canvas.mpl_connect(
            "key_press_event", lambda event: key_press_handler(event, canvas, tb))
        axbox = canvas.figure.add_axes([0.1, 0.05, 0.8, 0.075])
        self._tb = TextBox(axbox, 'label')

qapp = QtWidgets.QApplication([])
app = ApplicationWindow()
app.show()
qapp.exec_()
```
diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
@@ -842,37 +842,38 @@ def _notify_change_observers(self):
 
     def begin_typing(self, x):
         self.capturekeystrokes = True
-        # Check for toolmanager handling the keypress
-        if self.ax.figure.canvas.manager.key_press_handler_id is not None:
-            # Disable command keys so that the user can type without
-            # command keys causing figure to be saved, etc.
-            self._restore_keymap = ExitStack()
+        # Disable keypress shortcuts, which may otherwise cause the figure to
+        # be saved, closed, etc., until the user stops typing.  The way to
+        # achieve this depends on whether toolmanager is in use.
+        stack = ExitStack()  # Register cleanup actions when user stops typing.
+        self._on_stop_typing = stack.close
+        toolmanager = getattr(
+            self.ax.figure.canvas.manager, "toolmanager", None)
+        if toolmanager is not None:
+            # If using toolmanager, lock keypresses, and plan to release the
+            # lock when typing stops.
+            toolmanager.keypresslock(self)
+            stack.push(toolmanager.keypresslock.release, self)
+        else:
+            # If not using toolmanager, disable all keypress-related rcParams.
             # Avoid spurious warnings if keymaps are getting deprecated.
             with cbook._suppress_matplotlib_deprecation_warning():
-                self._restore_keymap.enter_context(
-                    mpl.rc_context({k: [] for k in mpl.rcParams
-                                    if k.startswith('keymap.')}))
-        else:
-            self.ax.figure.canvas.manager.toolmanager.keypresslock(self)
+                stack.enter_context(mpl.rc_context(
+                    {k: [] for k in mpl.rcParams if k.startswith("keymap.")}))
 
     def stop_typing(self):
-        notifysubmit = False
-        # Because _notify_submit_users might throw an error in the user's code,
-        # we only want to call it once we've already done our cleanup.
         if self.capturekeystrokes:
-            # Check for toolmanager handling the keypress
-            if self.ax.figure.canvas.manager.key_press_handler_id is not None:
-                # since the user is no longer typing,
-                # reactivate the standard command keys
-                self._restore_keymap.close()
-            else:
-                toolmanager = self.ax.figure.canvas.manager.toolmanager
-                toolmanager.keypresslock.release(self)
+            self._on_stop_typing()
+            self._on_stop_typing = None
             notifysubmit = True
+        else:
+            notifysubmit = False
         self.capturekeystrokes = False
         self.cursor.set_visible(False)
         self.ax.figure.canvas.draw()
         if notifysubmit:
+            # Because _notify_submit_observers might throw an error in the
+            # user's code, only call it once we've already done our cleanup.
             self._notify_submit_observers()
 
     def position_cursor(self, x):
